TIME RELATIONS OF THE ORGAN RESPONSE. 577 



I5C 



100 



\ 



indirect and direct excitation. 1 A suggestive fact in connection with the 

 delay which occurs in the response of the organ to the passage of an excit- 

 ing current through its substance, is the minimal duration of the period. 

 This, in Torpedo, Malapterurus, and skate, is '003 sec., a time identical 

 with the nerve-ending time in motor nerves, as ascertained by Bern- 

 stein. The delay is prolonged by lowering the temperature, the minimal 

 limit of '003 sec. at 30 C. being in all the above organs increased, until 

 at 5 C. it may amount to '01 sec. Here, again, the alteration is one which 

 affects almost equally the delay to the so-called " direct," as that due 

 to indirect, stimulation. From the above remarks, it will be clear that 

 the writer considers the term " direct," as applied to the stimulation of 

 a portion of organ by the passage through it of an electrical current, to 

 be inappropriate ; the passage of a current through the substance of the 

 organ acts by exciting the contained nerves. 



When the response begins, it develops in Torpedo organ with great 

 rapidity, reaching its maximum in 0'003 sec. under favourable condi- 

 tions. 2 The rate of development is accelerated by warmth, and slowed by 

 cold. This is seen by the curves given 

 in Fig. 293, which are plotted from a 50 o 

 number of rheotome observations ob- 

 tained in the organ of Torpedo by uo 

 myself. In Malapterurus the develop- 500 

 ment may be completed in less than 

 0-002 sec. at 30 C. The magnitude of w> 

 the change in this organ is increased 

 by cold, and diminished by heat (see 

 Fig. 294). 



The subsidence of the electromotive 

 change of the response is slower than 

 the development, occupying 0'005 sec. 

 at 15 C., and O'Ol sec. at 5 C. In the 

 final stages it is generally much pro- 

 longed, each response being thus ac- 

 companied by an after-effect, having 

 the same sign as the response itself. 

 It is for this reason that, after a rapid series of responses, a more 

 or less persistent electromotive change presents itself, having the 

 same sign as that of the response, the so-called organ current of 

 du Bois-Eeymond. Attention may here be drawn to the fact that the 

 subsidence is not caused by any counter-effect, due to changes occurring 

 in more remote parts. In both muscle and nerve, with contacts on 

 uninjured tissue, the change under the contact proximal to the seat of 

 excitation having been propagated to the distal region, is counteracted 

 by a second change of like sign under this distal portion. The total 

 effect under any one contact in these tissues is thus diphasic, i.e. the 

 response is one in which the initial change rapidly subsides through the 

 development of one of opposite sign counteracting it. In the electrical 

 organ there is no such counter-effect, because there is no protoplasmic 

 continuum along which the excitatory change can be propagated, and 



1 Garten, CentralU. f. Physiol., Leipzig u. Wien, 1879, Bd. xiii. S. 1. 



2 Schonlein has found that the development of the change in the organ of vigorous 

 Torpedoes may take place in less than 0'002 sec. (Ztschr. f. Biol., Munchen, Bd. xxxiii. 



S. 408). 



VOL. ii. 37 



0*005 OX)I Ot>2, 0-O3 



Eocc 



FIG. 293. The ordinates indicate the 

 galvanometric deflections when the 

 galvanometer was connected with a 

 strip of torpedo organ for '002 sec. 

 at various intervals after the excita- 

 tion of the strip, which occurred 

 at 0. 



